Palmetto Preventive
Laboratory test

T4

Evaluates thyroid hormone (T4) levels.

About this test

T4 measures thyroxine, a thyroid hormone, and helps interpret thyroid function with TSH.

Common reasons for testing

  • Clarifying an abnormal TSH result.
  • Monitoring thyroid disease in situations where TSH alone is insufficient.

These are examples of clinical uses. Your history and symptoms determine whether testing is appropriate.

What to expect

A small blood sample is taken from a vein in your arm. You may feel a brief pinch and have mild bruising. Tell the person collecting your sample if you have fainted with needles or take a blood thinner; keep pressure on the site afterward.

Appointment length

Your visit is expected to take about 15 minutes at our West Ashley location.

Categories

Thyroid Health

Preparation

  • Ask how to time the blood draw relative to your thyroid medicine; keep the timing consistent for follow-up tests.
  • Biotin in hair, skin, and nail supplements can distort some thyroid results. Ask the laboratory whether a pause is needed and for how long; the answer depends on the dose and assay.
  • Bring a list of medicines and supplements, including biotin, vitamins, and hormones. Do not stop or change prescribed medicines unless your clinician tells you to.

Order requirement

No outside order needed

Understanding your results

  • Total T4 and free T4 are different tests. Pregnancy and binding proteins can affect total T4.
  • Confirm which measurement your clinician ordered.

What happens next?

Review the report with your clinician alongside your symptoms, medical history, and earlier results. A value outside the reference range does not always mean disease, and a normal result does not explain every symptom. Confirm who will arrange any repeat or additional testing.

Sources & further reading

This patient summary draws on published clinical literature and professional guidance. Patient resources are identified separately below. Preparation also depends on your specific order and the collecting laboratory or imaging team.

Content updated October 11, 2026. General education; individual advice comes from your care team.

Transparent pricing

Know the cost before your visit

Palmetto Preventive is a direct-pay service. You will see clear payment terms before your booking is finalized — no surprise lab bill.

Self-pay price

$50.00

One transparent price for this test. Payment terms are presented before your booking is finalized.

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Our pricing promise

Transparent self-pay pricing — you see the price before you book.

No surprise lab bill after your visit.

If testing is not approved, your payment is refunded in full.

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